Polymerization of unsaturated aldehydes



zation products which are characterized b bein I s fusible and readily soluble in a wide'var iety. (CHFC organic and other solvents, and it also relates to t such new and useful polymers d polymer prod is the lowest member. These unsaturated aldeucts. I hydes are conveniently represented by the gen- Manyunsaturated aldehydes, such as methaera-1 formula crolein and related alpha-substituted acroleins 1o 30 solvents such as the alcohols, esters, ketones, aro-- inhibiting the undesired aumpolymem' 30 Patented Aug. 27, 1940 I I I UNITED ST TES PATENT OFFICE rotmalzarloiv or UNSATURATED mamas Clyve C. Allen, Berkeley, Calib, 'assignor to Shell Development Company, San Francisco, Calif a corporation of Delaware NoDrawing. ApplicationNovember8,1937,

SerlalNo.173,535

12 Claims. (01. 260-67) This'invention relates to a process for eirecting ularly susceptible .to autopolymerization to usethe polymerization of readily polymerizable un-- less polymers embraces the group of alpha-substisaturated aldehydes to new and useful polymerituted acroleins of which methacroleln as well as. some beta-substituted acroleins, in the R pure state or in common solvents, are very unwherein e m carbon t i t rtiary, that is,

stable being particularly susceptible to autopolylink ed t th is m merization resultingin the formation of infusible an g b 33 3?? mg gg m izgi cal and insoluble solid polymers of little or no value. as methyl, ethyl, pr'opyl, butyl, amyl, etc.; all w W hue such readily autopolymel'izable unsatu" alkenyl radical as ethenyl, propenyl, butenvl, etc.; ratedaldehydes have been regarded as potentially an m or aralkyl radical as phenyl benzyl phenvaluable raw materials in the production of useful methyl, naphthyl, t' xylyl, 1 a u ycnc 22 3 materials: and attempts have radical as cyclopropyl, cyclobutyl, cyclopentyl 31 t Y i tendency these and the like as well as suitable substitution prodme sa g g 3: nets of the above radicals and their homologues met with no 6 Po ese empts have and analogues. -As examples of suitable substisuccess- I tuted hydrocarbon radicals, R. may represent rad- It is an object of this invention to provide a icals such ,g &0 1, cm cmon,

method in accordance with which such readily H: CH

autopolymerizable unsaturated aldehydes may F COOH' be readily and substantially completely converted 0l to valuable polymers which are fusible and substantially soluble in a wide variety of organic n t like;

matic hydrocarbons, etc., and which are us ful tion reaction during the execution of the process in the manufacture or coatings, iilms, threads, w v e desired p y e i i n of the unsetdiscs, molded articles, joining materials, and th urated aldehyde to fusible soluble products is e!- like. I fected, any sufliciently effective member of the 3 The process of the invention comprises effectclass of silb'stflmes knOWn t0 h art as anti-408i- 5 ing the desired polymerization reaction or reacd nts may be used. It is only ne y that the tions which will yield the valuable polymers hereselected agent b efleet ve to substa t ally in described in the presence otautopplymeflzgr hiblt autopolymerization of the unsaturated aldetion inhibitors andunder such conditions that hyde during the. execution of the proce 1 h in the occurrence of the undesirable autopolymeriinvention- Am s'th ors ni inh i r wh 40 l zation yielding infusible, insoluble products is may he s c u e plo ed a e t p e inhibited or prevented. By operation in this u s. the a s, t e organic hydroxy manner. the readily autopolymerizable unsatuamino compounds, the mercaptans and the like. rated aldehydes to which this invention relates suitable amines are e p y. secondary nd 4? can be converted in practical yields tosoluble rt a y'a p h a 83811171 amines 88 e fusible polymer products. methyl amines, the ethyl amines, the propyl The class of unsaturated aldehydes which may am n s, h m x d lkyl m n h as ethy be polymerized to soluble thermoplastic polymers propyl amine, etc., benzyl amine, the aromatic in accordance with the invention embraces unamino compounds such as aniline, the toluidines, to saturated aldehydespossessingin their structure the xylidines, methyl aniline, trlphenyl amine, an unsaturated tertiary carbon atom linked dithe phenylene diamines and the like and their rectly to the aldehyde group, and halogen substihomologues, analogues and suitable substitution tuted acroleins such as alpha-chloracrolein, betaproducts. Representative suitable organic hy-- chloracrolein and the like. A preferred sub-' droxy amino compounds are among others; the class of unsaturated aldehydes which are partic- 'alkylolamines as monoethanolamine, diethanolamine, triethanolamine, the mono-, diand tripropanolamines, -butanolamines, -pentanolamines, etc.; the aldehyde-ammonia and aldehyde-amine condensation products such as acetaldehyde-ammonia, isobutyraldehyde-ammonia, benzaldehyde ammonia, acetaldehyde methyl amine, acetaldehyde-aniline, etc.; the amino phenols, the amino naphthols, the amino cresols and ical and at least one hydroxy group linked to a carbon atom embraced in the nucleus of an arcmatic radical. A phenolic compound may be monohydric or polyhydric and one or more hydrogen atoms thereof may be replaced by suitable inorganic or organic substituents. Suitable phenolic compounds are, among others, the following: phenol, the cresols, the naphthols, the anthrols, the xylenols, cumenol, carvacrol, thymol, eugenol, catechol, resorcinol, hydroquinone, orcinol, guaiacol, phloroglucinol and the like and their hcmologues, analogues and suitable substitution products.

The invention is not limited to the use of any specific amount of the autopolymerization inhibitor. It is only necessary that the specific inhibitor or mixture of inhibitors be present in an effective amount. What is an effective amount will depend upon the specific inhibitor used, the particular unsaturated aldehyde polymerized, and the conditions under which the polymerization operation of the invention is executed.

45 In the majority of cases, and particularly when the inhibitor is. a phenolic compound, the stabilizers have the desired effectiveness when employed in concentrations of from about 0.002% to about 2% by weight of the unsaturated material treated.

As an example of a suitable mode of executing the process of the invention, the following procedure may be followed. The unsaturated aldehyde .from any convenient source is stabilized against autopolymerization by incorporating therewith a stabilizing amount of an autopolymerization inhibitor, and the stabilized aldehyde is charged to a suitable reaction vessel. In the case of the very readily autopolymerizable unsaturated aldehydes, for example, methacrolein, it may be desirable to incorporate the autopolymerization inhibitor with the freshly distilled alvdehyde just before effecting the desired reaction.

merization of the unsaturated aldehyde to a fusible polymer product which is substantially soluble in oxygenated organic solvents and aromatic hydrocarbons occurs.

A preferably employed reaction vessel comprises a kettle of the desired size equipped with mechanical stirring or agitating means and means for heating or cooling its contents. The reaction is preferably eflected with the unsaturated aldehyde in the liquid phase. The reaction may or may not be effected in the presence of a solvent or diluent. For example, the polymerization may be effected in the presence of water and/or other solvent or diluent materials as alcohols, ethers, hydrocarbons, etc., which are preferably inert with respect to the unsaturated aldehyde and autopolymerization inhibitor under the conditions at which the desired polymerization reaction is to be effected.

Any suitable polymerization agent which is ca pable of inducing the desired polymerization of the stabilized unsaturated aldehyde to the desired soluble and fusible polymer product may be used. Basic polymerization agents such as the basic oxides, basic hydroxides, basic-acting salts and the like are advantageously employed in the majority of cases. A particularly suitable group of basic polymerization agents includes the alkali metal oxides, the alkali metal hydroxides, the alkali metal alcoholates and the basic-acting alkali metal salts, which agents are preferably employed in the temperature range of from about l C. to 50 C. The polymerization agents may be employed per so as solids, or they may be applied in solution in water or other suitable solvents therefor. For example, the alkali metal hydroxides and alcoholates are conveniently employed as solids, in concentrated aqueous solution, or in alcoholic solution. Conveniently employed basic salts are the alkali metal cyanides. They are preferably employed in aqueous solution or alcoholic aqueous solution.

The desired polymerization reaction is preferably executed at temperatures below about 50 C. and at about atmospheric pressure, although higher temperatures and pressures may 'be used when necessary ordesirable. The temperature to be employed in each particular case is dependent upon the particular unsaturated aldehyde polymerized, the particular polymer product desired, the particular polymerization agent, and the form in which the particular polymerization agent is employed. Aqueous and solid alkali metal hydroxides may be advantageously used at temperatures'of from about 0 C. to. about 50 C. Alcoholic potassium hydroxide has been successfully used at temperatures as low as from about -5 C. to +5 C. When alkali metal hydroxide solutions are employed the temperature is easily controlled and the formation of useless polymer products avoided by adding the stabilized unsaturated aldehyde to the well-agitated and cooled caustic solution. In general, rather large proportions of the basic polymerization agent are employed so that disproportionation can take place at a relatively fast rate over and above other reactions.

At the conclusion of the polymerization reaction, the polymer product may be recovered from the reaction mixture in a variety of suitable manners obvious to those skilled in the art. Suitable representative modes of recovery are described in detail in the specific examples.

For the purpose of making the invention clear and readily understandable, it will be described 15 with particular reference to its application to the polymerization of methacrolein (CHFC-CHO H: a typical and readily available unsaturated aldehyde of the class to which the process of the invention is applicable, to valuable polymer products which are fusible and soluble in a wide yeti-- ety of solvents. It is to be understood that the same principles and mode of operation are applicable to the treatment of the other members of the class of unsaturated aldehydes herein described, and that there is no intent to restrict the 1 merization reaction is inhibited while other po1y-' Y merization reactions of the Cannizzaro, aldol and xb'snzoin type which yield valuable fusible and soluble polymer products are made to take place exclusively or at least to very materially predominate.

The methacrolein polymers obtained in accordance with the process of the invention in the presence of different autopolymerization inhibitors and difierent polymerization agents under differ,- ent polymerizing conditions are similar in physical as well as chemical properties. They appear to consist for the most part of polymerized unsaturated glycol esters and unsaturated glycols with smaller amounts of polymerized unsaturated acids. The polymer products are fusible. -The softening point appears to be a function of the average molecular weight of the polymer product obtained. The polymers are in general readily soluble in oxygenated organic solvents such as alcohols (ethanol, butanol, etc.), ketones- (acetone, methyl ethyl ketone, methyl hexyl ketone, etc.), esters (ethyl' acetate, butyl acetate, etc.) and aromatichydrocarbons (benzol, xylol, etc.). They are substantially insoluble in water and aliphatic hydrocarbons.

The following specific examples further illustrate the nature and mode of execution of the invention. The examples are not to be taken as limiting the invention to the particular reactants, proportions and products specified.

Erample I zoyl peroxide for about 8 hours.

The au-- aromatic hydrocarbons.

acid and refluxed with a small amount of benlution was run into cold water. Theflbrous resin precipitated was washed with water and dried under' vacuum.

About 152 gm. of the piu'ified product were obtained, representing a yield of about 90.5% on the applied methacrolein.

The product was a brittle fusible solid having a softening point of from about 25 C. to 70 C. It was substantially insoluble in waterand aliphatic hydrocarbons, and only partially soluble in ethers. It was completely soluble. in alcohols, esters and aromatic hydrocarbons from which solutions it forms clear adherent films.

The polymer product had, a molecular weight of about 367, corresponding t'o the polymerization of five molecules of methacrolein and attachm'ent of one molecule of water. The prodnot analyzed as follows:

. Per grams The cooled so- Acid equivalents 0.044 Hydroxyl equivalents 0.120 Carbonyl equivalents 0.157 Saponiflable equivalents 0.225

Example II About 168 gm. (2.4 mols) of methacrolein were stabilized against autopolymerization by moor-- porating therewith about 0.7% of hydroquinone. The stabilized methacrolein was added to about 1000gm. of an aqueous 40% sodium hydroxide solution dropwise over a period of about 3 hours,

the mixture being vigorously stirred and mainand the filtrate evaporated to dryness under vacuo. The residue was a semi-resinous material weighing about gm.

The product at this. stage was water soluble. It was dissolved in water and acidified with hydrochloric acid whereupon about 100 gm. of an =acid-insoluble resin was precipitated. The pre-, cipitated resin was dissolved in ethyl alcohol and the resulting solution refluxed with benzoyl peroxide for about 8 hours. The polymer was then precipi ted from the alcohol solution by pouring it in o a boiling aqueous 3% hydrochloric acid solution.

The polymer productwas a fusible solid melting from about 50 C. to 100 C. It was substantially insoluble in water and aliphatic hydrocarbons, and only sparingly soluble in ethers. It was readily soluble in alcohols, esters, ketones and Analysis showed. the product to be very similar in composition to the product described in, Example I.

Example III About 168 gm. of methacrolein-which had been previously stabilized by the addition thereto of about 0.7% of hydroquinone were vigorously,

product treated with hydrochloric acid to recover the product as described in Example The .polymer product, which had substantially the characteristics of the polymer obtained in accordance with the operation of Examples I and II, was obtained in good yield.

Substantially the same type of polymer product was obtained when methacrolein, which had been stabilized against autopolymerization, was polymerized by treatment with sodium methallylate at about 0 C. in the manner above described.

Ea'ample IV About 84 gm. (1.2 mols) of methacrolein were stabilized against autopolymerization by the addition thereto of about 0.7% of hydroquinone. The stabilized methacrolein was dissolved in about 500 c. c. of 95% ethyl alcohol and the resulting solution stirred and maintained at a. temperature of about -5 C. to +5 C. while about c. c. of a 33% alcoholic (ethyl) potassium hydroxide solution was added thereto dropwise over a period of about 2.5 hours. All of the methacrolein was reacted under these conditions. We.- ter was then added, and the alcohol was removed by distillation whereby a part of the polymer product precipitated. After substantially all of the alcohol had been removed, the residue was extracted with ether and the ether extract evaporated. The ether extract yielded about 46 gm. of polymer product as a residue (Sample I). The aqueous residue remaining after the ether extraction was made acidic (about 5N) by addition of concentrated hydrochloric acid and again extracted with ether. The evaporation of thisfinal ether extract solution yielded about 44 gm. of polymer product (Sample II). The final aqueous residue, after removal of dissolved ether, contained only traces of organic matter.

Analyses of the products were as follows:

Sample I Sample II Molecular weight (acetic acid) 240 184 Acid No. (equivalents per 100 gm) 0. 062 0.0115 Saponiflcation N o. (equivalents per 100 1.1-". "we; 335% 32% Ace 1N0. (equiv en s per g Car nyl value (equivalents per 100 gm.) 0. 66 0.10

The polymer products were liquids insoluble in water and soluble in the common organic solvents including aliphatic hydrocarbons.

Example V About 84 gm. (1.2 mols) of methacrolein were stabilized by mixing therewith about 0.7% of hydroquinone. The resulting stabilized mixture was dissolved in about 500 c.c. of benzol. This solution was stirred and maintained at about 0" C.

while about 20 gm. of a 3N solution of sodium' methallylate were added to it dropwise. The mixture was then allowed to stand for about 20 hours while gradually warming to room temperature. At the end of this time, 500 c.c. of water were added and the benzene removed by azeo- Example VI About 168 gm. (2.4 mols) oif methacrolein were drocarbons.

stabilized against autopolymerization by the in.- corporation therewith of about 0.7% of hydroquinone. The thus stabilized methacrolein was added dropwise to a well stirred solution consisting of about 250 c.c. of ethyl alcohol, 200 c.c. of water, and 28 gm. (0.43 mol) of potassium cyanide, which was maintained at a temperature of about 40 C. The addition of the methacrolein required about 2 hours. The reaction vessel was capped by a well-cooled (acetone-solid carbon dioxide) reflux condenser. After the addition of the methacrolein, the reaction mixture was refluxed for about 4 hours. Under these conditions, all but a trace of the methacrolein reacted to give a homogeneous reaction mixture.

The polymer product may be recovered from the reaction mixture in a variety of suitable manners, the method of recovery apparently having little influence on the character of the isolated polymer product. In this particular case, 0.43 mol of concentrated hydrochloric acid was added and after refluxing for a few minutes, the mixture separated into two layers. Water was removed from the crude product by the addition of ether and calcium chloride. The alcohol was then distilled oil and the residue vacuum distilled to a temperature of about 215 C. under'a pressure of about 5 mm. of Hg.

The distillate (about 52 gm.) had a molecular weight of about 212 "(in benzene). It was soluble in oxygenated organic solvents and aromatic hy- It was insoluble in water, and only slightly soluble in aliphatic hydrocarbons. The product corresponded closely to the product which should be obtained by the condensation of three molecules of methacrolein plus one of water.

The bottoms (residue of the vacuum distillation) which weighed about gm. consisted of a polymer product having a molecular weight of about 660 (in benzene). It was readily soluble in oxygenated organic solvents and aromatic hydrocarbons, but insoluble in water and aliphatic hydrocarbons. This main polymer product appears to be a mixture corresponding to the formula (C4HaO)1v.I-I2O and having 1 hydroxyl group, 1 to 1.5 reactive carboxyl groups, and 1 to 2 unreactive oxygen atoms per formula weight.

In each of the operations described in the above examples, substantially the same results are ob-, tained when an eiifective amount of some other anti-oxidant or autopolymerization inhibitor is used in lieu of hydroquinone. Representative inhibitors such as pyrogallol, the cresols, the naphthols, resorcinol, ethanolamine, acetaldehydeammonia, aniline, amino phenol, phenylene diamine, copper, copper alloys, sulphur, selenium, tellurium, the halogens, etc.; are very suitable and their use results in polymer products having the same general character as those described in the examples. Comparable results are also obtined when other active polymerizing agents such as the basic oxides, other basic metal hydroxides,

other alcoholates, the phenolates and other basic salts are employed in the execution of the proces of the invention.

I claim as my invention:

1. A process for the production of valuable fusible and soluble polymers from autopolymerizable unsaturated aldehydes of the group consisting of alpha-substituted acroleins containing an unsaturated tertiary carbon atom linked directly to the aldehyde group and the alphaand beta-substituted acroleins wherein the substituent is a halogen atom which comprises adding which comprises adding an autopolymerization.

inhibitor to the unsaturated aldehyde in a stabilizing amount up to about 2% by weight of the aldehyde, and treating the thus stabilized unsaturated aldehyde with a basic polymerization agent under polymerizing conditions whereby the unsaturated. aldehyde undergoes polymerization to yield a fusible polymer product which is sub-: stantially soluble in oxygenated organic solvent and aromatic hydrocarbons.

3. A process for the production of valuable fusible and soluble polymers from unsaturated. aldehydes possessing an olefinic linkage between two aliphatic carbon atoms one of which is tertiary and linked directly to the aldehyde group which comprises adding a phenolic compound to the unsaturated aldehyde in a stabilizing amountup to about 2% by weight of'the' aldehyde, treating the thus stabilized unsaturated aldehyde with a basic compound selected from the group consisting of the alkali metal oxides, hydroxides, alcoholates and basic salts at a temperature of from about -10 C. to about 50 C. whereby the unsaturated aldehyde undergoes polymerization to yield a fusible polymer product which is substantially soluble in oxygenated organic solvents and aromatic hydrocarbons, and recovering the polymer product from the reaction mixture.

'4. A process for. the production of valuable fusible and soluble polymers from unsaturated aldehydes possessing an olefinic linkage between two aliphatic carbon atoms one of which is tertiary and linked directly to the aldehyde group which comprises adding hydroquinone to the unsaturated aldehyde in a stabilizing amount up to about 2% by weight of the aldehyde, treating the thus stabilized unsaturated aldehyde with an alkali metal hydroxide at a temperature .of from about C. to about 50 C. whereby the unsaturated aldehyde undergoes polymerization to yield a fusible polymer product which is substantially soluble in oxygenated organic solvents and aromatic hydrocarbons, and recovering the polymer product from the reaction mixture.

5. A process for the production of valuable fusible and soluble polymers from methacrolein which comprises adding an autopolymerization inhibitor to methacrolein in a stabilizing amount up to about 2% by weight of the methacrolein, treating the thus stabilized methacrolein with a basic polymerization agent under polymerizing conditions whereby it undergoes polymerization to yield a fusible polymer product which is substantially soluble in oxygenated organic solvents and aromatic hydrocarbons, and recovering the polymer product from the reaction mixture.

6. A process for the production of valuable fusible and soluble polymers frommethacrolein which comprises adding a phenolic compound to methacrolein in a stabilizing amount up to about 2% .by weight of the methacrolein, treating the thus stabilized methacrolein with a basic compound selected from the group consisting of the alkali metal oxides, hydroxides, alcoholates and basic salts at a temperature not greater than about 56 C. whereby the methacrolein undergoes polymerization to yield a fusible polymer productwhich vis substantially soluble in oxygenated organic solvents and aromatic hydrocarbons, and recovering the polymer product from the reaction mixture.

7. A process for the production .of valuable fusible and soluble polymers from methacrolein which comprises adding hydroquinone to methacrolein. in a stabilizing amount up to about 2% by weight of the. methacrolein, treating the thus stabilized methacrolein with sodium hydroxide at a temperature not greater than about 50 C. whereby the methacrolein undergoes polymerization to yield a fusible polymer product which is substantially soluble in oxygenated organic solvents and aromatic hydrocarbons, and recovering the polymer product from the reaction mixture.

8. A. process for the production of valuable fusible and soluble polymers from methacrolein which comprises adding hydroquinone to methacrolein in a stabilizing amount up-to about 2% by weight of the methacrolein, treating the thus stabilizing methacrolein with potassium cyanide at a temperature of about 40 0. whereby it undergoes polymerization to yield a fusible polymer product which is substantially soluble in oxygenated organic solvents and aromatic hydrocarbons, and recovering the polymer product.

9. In a process for treating methacrolein with a basic polymerization agent underpolymerization conditions to effect its polymerization to a fusible polymer product which is substantially soluble in oxygenated organic solvents and aromatic hydrocarbons, the step of controlling the polymerization so as to form in predominating amount the desired polymer product by incorporating an autopolymerization inhibitor with the methacrolein in a stabilizing amount upv to about 2% by Weight of the methacrolein.

10. The product prepared according to the process of claim 1.

11. The product prepared according to the process of claim 2.

1-2. The product prepared according to the process of claim 5. v CLYVE C. ALLEN. 

